1. Field of the Invention
The present invention relates to an image forming apparatus using electrophotographic technique.
2. Description of the Related Art
In-line type/tandem type image forming apparatuses including a plurality of image forming stations arranged approximately in line are known as electrophotographic image forming apparatuses (hereinafter, referred to as image forming apparatus) for forming multi-colored or full-colored images using electrophotographic technique.
In such image forming apparatuses, the image forming stations are each used to form images indifferent colors (e.g., yellow, magenta, cyan, and black), and the resulting monotone images are superposed to one another to form a multicolor image, which is transferred and fixed to a recording material to obtain an image.
The image forming stations are each configured with process units each including an image bearing member (hereinafter, referred to as photosensitive drum), a developer supply unit, a developing unit, a charging unit, a cleaning unit, an exposure unit, and a transfer unit. Some apparatuses are known to have a part of the process units in the form of a cartridge replaceable by a user for enhancing maintainability of the apparatuses.
Specific examples commonly used include a developing device configured as a replaceable development cartridge with developer therein, and a detachable process cartridge configured with a photosensitive drum, a developer supply unit, a developing unit, a charging unit, and a cleaning unit.
An intermediate transfer member in the form of an endless belt (with no ends) is known as a unit configured to transfer monotone images to a recording material. In apparatus having the unit, monotone images are primarily transferred to the intermediate transferring member one by one, and the resulting multicolor images superposed on the intermediate transferring member are secondarily transferred to a recording material.
A recording material conveyance member in the form of an endless belt (with no ends) is known as another unit configured to transfer monotone images to a recording material. In such an apparatus, recording materials are conveyed to each of image forming stations one by one, and the resulting images are directly transferred and superposed on the recording material. Hereinafter, the intermediate transfer member and the recording material conveyance member are collectively called an endless belt.
Some image forming apparatuses described above include a supporting member (hereinafter, referred to as a drawer) that is movable between inner and outer positions of the body of the apparatus for enhancing maintainability of the apparatus, the drawer being configured with image forming stations arranged therein (hereinafter, referred to as a drawer structure). A user pulls out the drawer for maintenance of the apparatus.
In the above described image forming apparatuses, any damage on photosensitive drum and endless belt (especially on an intermediate transferring member) may cause poor image quality. To prevent the damage on photosensitive drum and endless belt, some structures are discussed for an image forming apparatus having a drawer structure, including a structure in which a drawer is pulled out after a photosensitive member is separated from an endless belt (U.S. Pat. No. 6,708,011), and another structure in which a drawer member is pulled out in a direction oblique to the direction of separation of a photosensitive member from an endless belt (U.S. Pat. No. 7,526,227).
However, in a structure in which a drawer is pulled out after a photosensitive member is separated from an endless belt (e.g., the structure in U.S. Pat. No. 6,708,011), the direction of the separation of the photosensitive member from the endless belt is generally orthogonal to the drawing direction of the drawer, which sacrifices operability.
For the separation of the photosensitive member from the endless belt, an exposure apparatus for example is disposed in the separation direction, and the separation is performed in a space that is prepared in advance between the drawer member and the exposure apparatus. This hinders downsizing of the apparatus.
In the structure in which a drawer member is pulled out in a direction oblique to the direction of separation of a photosensitive member from an endless belt (U.S. Pat. No. 7,526,227), the drawer member is linearly operated for enhancing operability. However, the linear operation requires a larger space, thus hindering downsizing of the apparatus.